Outline of talk for Snowmass

1. Outline of talk for Snowmass Introduction: studies performed to optimise detector design parameters this talk: effect of varying beam pipe radius: 3 values: 8, 15, 25 mm comparison of long-barrel (LDC) with short-barrel + endcaps (SiD) vtx det Vertex charge as tool for physics: examples: left-right forward-backward asymmetry ( S. Riemann) background reduction in multijet events Reconstruction method for vertex charge: event sample, definition of L/D, Qvtx, MPt, eb, l0 show lpm, l0 as fct of eb – point out that l0 is used to quantify performance, since it determines how well background can be suppressed, if background is high, for the gold-plated cases, in which b-quarks hadronise to B+-

2. Effect of varying CM energy: at low sqrt(s) average track momentum lower (mult scattering!) & seed vertex closer to IP (plots of Ldec vs sqrt(s), l0 vs Ldec & percentages of vertices in beam pipe and between vtx det. layers at different energies (50 .. 500 GeV))  Qvtx reconstruction more challenging at lower energies Polar angular dependence: plot l0 vs cos q at 4 energies (see last Phys. Mtg), for standard detector: poorer performance at low sqrt(s) & large cos q , as expected Varying the beam pipe radius: introduction with schematics of the 3 detectors compared, point out that beam pipe needs to be thicker if its radius is larger, for mech. integrity; plot of l0 vs (L/D)min, & cut values chosen for the 3 detectors (0.17, 0.18, 0.19) plot l0 vs cos q comparing the performance of the 3 det’s at sqrt(s) = 100 GeV: l0 increases from ~ 9.5% to ~ 12.5% when going from standard to large Rbp vtx detector, in a typical cos q bin (0.2 < cos q < 0.25)

3. Plots summarising Rbp comparison: l0 vs sqrt(s) in 2 bins of cos q : (0.2, 0.25), (0.85, 0.9), in central part of det, difference standard – large Rbp det more pronounced, at the edge, difference between standard and small Rbp det is larger l0 vs sqrt(s) averaged over 0 < cos q < 0.9 (relevant for multijet processes): at lower energies, difference between detectors is larger Translating l0 values into effective luminosity: introduce n-jet luminosity factor, quantifying how much more integrated luminosity the detectors with changed Rbp would need compared to the standard detector (small radius det yielding factor below 1); obtained from increasing Ldec cut until l0 of ‘less good’ detector agrees with that of ‘better’ detector; { in practise, one would use events with lower Ldec with reduced weight – would expect weight to be close to 0 if background >> signal } plots of 2- and 4-jet luminosity factors, at sqrt(s) = 100 GeV (& possibly 50, 500 GeV, if time permits – values for those energies currently in preparation): at 100 GeV, factors are 1.6 (Rbp = 25mm) and 0.7 (Rbp = 8 mm), respectively

4. Comparison with SiD detector: SiD short-barrel + endcaps vertex detector, inserted into the same ‘global detector’ geometry used for LDC detector (TESLA geometry) plots ofl0 vs cos q at sqrt(s) = 100 GeV and energy dependence of cos q average (as for Rbp comparison): results still in preparation; plot to determine L/D cut showed overall performance very similar to standard det., comparison in terms of cos q dependence in preparation